JP4616244B2 - Optical disc recording method and optical disc apparatus - Google Patents

Description

  The present invention relates to an optical recording method and an optical disc drive apparatus for driving and controlling an optical modulation waveform when information is recorded on an information recording medium.

  Many types of recordable optical discs such as CD-R / RW, DVD-RAM, DVD ± R / RW, Blu-ray Disc (BD) -R / RE, and HD DVD have been commercialized and widely spread. Yes. In a recordable optical disk device, a method called Optimum Power Control (OPC) is used to always record user data with an appropriate recording power against fluctuation factors such as temperature, light source wavelength, and medium manufacturing variations. The recording power is calibrated for each medium.

The following are known OPC systems.
(1) OPC method mainly for write-once discs As an example of the OPC method using asymmetry, JP-A-6-139574 discloses asymmetry of the shortest mark and space repetition signal and asymmetry of the longest mark and space repetition signal. An OPC technique of making the two equal is disclosed.

(2) OPC method mainly for rewritable discs As an example of the OPC method that uses the signal modulation factor (or reflectivity), Japanese Patent Laid-Open No. 2000-306241 discloses the maximum change in reflectivity with respect to the change in recording power. An OPC technique for obtaining a recording power by multiplying a power by a coefficient is disclosed. Further, Japanese Patent Laid-Open No. 2003-067925 discloses an OPC technique in which the recording power is determined using the slope of the change in modulation degree with respect to the recording power itself or the slope of the change in γ value.

  FIG. 1 is a schematic diagram illustrating the γ method. Here, the γ value is a value normalized by the change rate of the modulation degree and the change rate of the recording power. In FIG. 1, the solid line is a curve representing the degree of modulation, and the broken line is a curve representing its differential value. There is a power Ptarget whose modulation degree increases as the power increases, but increases rapidly as the mark is formed. Since the power multiplied by the coefficient from the power in the vicinity becomes the maximum point of the margin, Ptarget is multiplied by ρ to obtain the optimum power PWO. This method is an index that is resistant to the recording power setting offset.

  There is a so-called κ method as an index of the same kind. Japanese Laid-Open Patent Publication No. 2002-298357 describes the κ method recommended in the BD standard. The recording power adjustment method using the κ method is based on the relationship between the recording power obtained by trial writing and the modulation degree obtained from the reproduction signal amplitude of the signal, and Ptaget, Mind, κ, and ρ set in advance on the optical disc. The optimum recording power is adjusted based on the value.

  FIG. 2 is a schematic diagram illustrating the κ method. First, the specified recording power corresponding to the specified modulation power Mind in the optical disc among the characteristics of the modulation power Mw from the plurality of types of recording power Pwm set at the time of trial writing and the reproduction signal amplitude of the signal recorded by each Pwm. An evaluation value Sm = Mm × Pwm is obtained in the range near Ptarget, and a recording power Pthr at which the degree of modulation becomes zero when the relational characteristic of Pwm and Sm is linearly approximated in this range is obtained. , Ρ, the optimum recording power Popt is obtained by calculating Popt = κ × ρ × Pthr.

JP-A-6-139574 JP 2000-306241 A Japanese Patent Laid-Open No. 2003-67925 JP 2002-298357 A

  Recording type optical discs are roughly classified into a write-once type using an organic dye material or the like as a recording layer and a rewritable type using a phase change recording material or the like as a recording layer. Furthermore, there are two types of rewritable optical discs, one that emphasizes compatibility with ROM discs and one that has a sector structure and emphasizes random access performance. Here, the difference in the OPC method depending on the recording material using BD-RE and BD-R discs will be explained.

  FIG. 3 is a diagram showing experimental results on the relationship between the recording power of the BD-RE disc and each evaluation index. 3A shows the relationship between recording power and jitter, FIG. 3B shows the relationship between recording power and modulation, and FIG. 3C shows the relationship between recording power and asymmetry. The recording power is normalized and shown with an appropriate recording power of 100%.

  FIG. 4 is a diagram showing similar experimental results regarding the relationship between the recording power of the BD-R disc and each evaluation index. Comparing the rate of change of asymmetry with respect to the change in recording power shown in FIG. 3 (c) and FIG. 4 (c), the rewritable type BD-RE has a relatively small rate of change, and the write-once type BD- It can be seen that R has a relatively large rate of change. This is caused by the difference in characteristics of the recording material. In the rewritable BD-RE, erasure occurs simultaneously with data recording. For this reason, when an attempt is made to increase the recording power to form a large mark, the effect of the excessive recording power (or erasing power) simultaneously reducing (erasing) the mark occurs, resulting in a recording mark corresponding to the change in recording power. The change in the size of becomes smaller. This is the reason why the rate of change of asymmetry with respect to the recording power is relatively small. On the other hand, in the BD-R, which is a write-once type, the recorded mark cannot be erased. Therefore, when the recording power is increased, the recorded mark formed as the thermal energy increases. This is the reason why the change rate of asymmetry with respect to the recording power is relatively large.

  As described above, the asymmetry with respect to the recording power, that is, the difference in the rate of change in the size of the formed recording mark also appears in the behavior of the jitter between the two. As is clear from comparison between FIG. 3A and FIG. 4A, the power margin of the BD-RE having a small change rate of the recording mark size with respect to the recording power is wider.

Therefore, as a BD-RE OPC method in which the rate of change of asymmetry with respect to recording power is small, the threshold power P _thr for recording is obtained from the modulation degree without using asymmetry, and this is multiplied by a predetermined coefficient. A method for obtaining an appropriate recording power is suitable. In addition, as a BD-R OPC method in which the rate of change of asymmetry with respect to the recording power is large, a method of directly obtaining an appropriate recording power by a method of obtaining a recording power at which the asymmetry becomes a predetermined value is generally used. However, as with the BD-RE, it is also possible to obtain an appropriate recording power based on the modulation degree.

FIG. 5 summarizes the OPC methods suitable for different recording materials. As described above, a conventional OPC method using a modulation degree and asymmetry is disclosed. Among them, the OPC method using the modulation degree has the following two characteristics.
1) Based on the degree of modulation representing only the formation of long marks.
2) Obtain the optimum recording power from the power scan result smaller than the optimum power.

  In other words, the long mark that is not easily affected by disturbance is used as a reference, and the situation near the optimum power is not considered.

  Considering the temperature characteristics of the medium, for example, in the κ method, the multiplication coefficient (κ, ρ) for obtaining the optimum power from Pthr may be different. If the multiplication coefficient for obtaining the optimum power is different, the position where the target recording power is located in the power margin changes. This optimum power is determined from the system margin, and if it is too high or too low, the system margin will be reduced.

  FIG. 6 is a schematic diagram showing the result of measuring the power margin of the BD-RE disc for each temperature with the write power obtained using the κ method being 100%. The κ method tends to require higher power at low temperatures and lower power at higher temperatures than OPC at room temperature. As a result, the power margin on the high power side becomes small at low temperatures, and the power margin on the low power side becomes small at high temperatures.

  An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an OPC method capable of always determining an appropriate recording power in response to a temperature change and an optical disk apparatus using the same.

  As described above, the rewritable optical disc has a small change rate of asymmetry with respect to the change of the recording power, so the OPC is performed based on the degree of modulation to determine the recording power. However, in the OPC method (κ method, γ method) using the modulation degree, the power obtained by the OPC may deviate from the optimum power when the multiplication coefficients κ and ρ are constant with respect to the temperature change.

  Therefore, in the present invention, the multiplication coefficient of the OPC method is held as a temperature-dependent multiplication coefficient. Then, the ambient temperature of the optical disk medium is measured, and the optimum recording power is obtained using a multiplication coefficient corresponding to the temperature.

  Alternatively, the relationship between the standard modulation degree and the asymmetry equivalent amount is held as standard data, and the relationship between the deviation from the standard data and the value of the multiplication coefficient of the OPC method is held. Then, the data pattern for power calibration is actually recorded and reproduced on the optical disk medium to obtain the relationship between the modulation degree and the asymmetry equivalent amount, and the corrected OPC method multiplication coefficient obtained based on the deviation from the standard data is obtained. To obtain the optimum recording power.

  According to the present invention, it is possible to provide an OPC system that determines an appropriate recording power in response to a temperature change, and to provide a highly reliable recording method and optical disc apparatus. The present invention is useful not only for a rewritable type but also for a write-once type optical disc.

  According to the present invention, even when there is a change in the ambient temperature, it is possible to ensure the accuracy of OPC using the degree of modulation and to ensure high reliability.

  Hereinafter, details of the present invention will be described using examples.

FIG. 7 is a schematic diagram showing a configuration example of an optical disc apparatus according to the present invention. The optical disk medium 100 is rotated by a motor 160. The CPU 140 detects the ambient temperature of the optical disc medium 100 with the temperature sensor 170. The memory 180 holds a table as shown in FIG. 8, and the CPU 140 calculates the OPC using the coefficients κ and ρ stored in this table. That is, in this embodiment, the coefficients κ and ρ of the κ method have temperature dependency. In the example of FIG. 8, κ = κ ₀ that is κ value at 25 ° C. and ρ = ρ ₀ that is ρ value at 25 ° C. are used as references, and ρ = 0.95 × at 0 ° C. that is lower than that. ρ _0, and at a high temperature of 50 ° C., κ = 1.05 × κ ₀ and ρ = 1.05 × ρ ₀ . For temperatures other than 0 ° C. and 50 ° C., coefficients κ and ρ having temperature dependence may be determined in the same manner.

  At the time of reproducing the optical disc 100, the laser power / pulse controller 120 controls the current flowing to the semiconductor laser 112 in the optical head 110 so as to generate the laser beam 114 so that the light intensity commanded by the CPU 140 is obtained. The laser beam 114 is condensed by the objective lens 111 to form a light spot 101 on the optical disc medium 100. The reflected light 115 from the light spot 101 is detected by the photodetector 113 through the objective lens 111. The photodetector is composed of a plurality of photodetecting elements. The reproduction signal processing circuit 130 reproduces information recorded on the optical disc medium 100 using the signal detected by the optical head 110.

  At the time of recording on the optical disc 100, the laser power / pulse controller 120 converts predetermined recording data into a predetermined recording pulse current and controls the pulsed light to be emitted from the semiconductor laser 112. In this embodiment, the recording power is set in accordance with the γ-type OPC, and coefficients having temperature dependence as shown in FIG. 8 are used as the coefficients κ and ρ at that time.

  A recording power determination method in this embodiment will be described with reference to the flowchart of FIG. The sequence shown in FIG. 9 is held in the memory 180 as a program. The CPU 140 executes the sequence shown in FIG. 9 using the program, table, and output of the temperature sensor 170 held in the memory 180.

  First, in order to start OPC, OPC parameters such as recording start power and recording end power for the disc, and recording parameters such as power scan information and storage information are acquired (S101). Next, a plurality of types of recording power PWm are set according to a predetermined condition, and a predetermined signal pattern is recorded in each test writing area of the optical disc, for example, an isolated 8T mark having a predetermined length is recorded (S102). ).

  The plural types of recording powers PWm, for example, read out the average optimum recording power in the disc stored in advance in the optical recording / reproducing apparatus or reproduce the average optimum recording power recorded in the information control area of the optical disc in advance. And set based on the average optimum recording power. As an example, a plurality of types of recording power setting values Dm (m is an integer, for example, m = 1, 2, 3,... 16) preliminarily stored in the optical recording / reproducing apparatus are read, and using each Dm, the formula PWm = (average (Optimal recording power) * Dm sets multiple types of recording power PWm.

  Next, the high envelope (Henv) and low envelope (Lenv) of the playback signal corresponding to each PWm is measured by playing back the area where the test was written, and defined by the expression Mm = (Henv-Lenv) / Henv The modulation degree Mm to be calculated is calculated (S103). The relationship between the modulation degree Mm and the corresponding recording power PWm is, for example, as shown in FIGS.

  Next, as shown in FIG. 2, the evaluation value Smn = Mm × Pwm in the κ method is calculated, and the relationship between the corrected recording power Pwm and the evaluation value Smn is linearly approximated in the vicinity of Mind (disc recommended modulation degree), The recording threshold power Pthr at which the modulation degree is zero, that is, the evaluation value is zero is calculated (S104). Next, referring to the temperature sensor value of the drive performing OPC, the κ and ρ values corresponding to the temperature are acquired from the table of FIG. 8 (S105).

  By using the calculated recording power threshold value Pthr and the multiplication coefficient acquired from the table of FIG. 8, the formula Popt = κ × ρ × Pthr is calculated to calculate the optimum recording power Popt (S106). Then, recording on the recording disk is performed using the optimum recording power Popt thus determined.

  10 and 11, recording is performed using the recording power obtained by the OPC of the present embodiment, and the relationship between jitter, SER (Symbol Error Rate) and power margin, which is a representative index of recording quality, is 0 ° C., 25 The results measured at 50 ° C and 50 ° C are shown. It can be seen that by introducing the table of FIG. 8, the power margin at each temperature is improved so as to match both jitter and SER. That is, the temperature margin can be widened by giving the multiplication coefficients κ and ρ temperature dependency. This effect was confirmed with other discs. The effect of changing the multiplication coefficient in accordance with the temperature is also effective for the γ method using the same modulation degree, and the ρ value of Popt = ρ × Ptarget is changed in accordance with the temperature as shown in FIG. As a result, even when the ambient temperature is different, the power margin during recording can be made the same.

  An embodiment in which the multiplication coefficient for temperature is not fixed with respect to temperature but is made variable with reference to asymmetry and modulation degree will be described. In this embodiment, information from the temperature sensor is not required.

  FIG. 13 is a diagram showing the results of measuring the relationship between asymmetry and modulation degree at 0 ° C., 25 ° C., and 50 ° C. For example, when the asymmetry is -5%, the degree of modulation differs at each temperature. In this embodiment, this relationship is used to sense temperature differences, recording state differences, etc., and change the coefficients κ and ρ to find the optimum power.

  Therefore, for example, the values of the modulation degree when the asymmetry measured by the reference drive device is −5% and 0% are tabulated in the reference database as the standard value modulation degree and stored in the memory area of the control software. In mass-produced drive devices, κ and ρ are changed as shown in FIG. 14 with reference to the reference database.

In the example of FIG. 14, the modulation degree M0 when the asymmetry is −5% and the modulation degree M1 when the asymmetry is 0% are registered in the reference database. The degree of modulation of the degree of modulation when the asymmetry is -5% and 0% with the drive device that is being observed is Mm0 and Mm1. If the measured modulation degree Mm0 satisfies 0.98 × M0 ≦ Mm0 ≦ 1.02 × M0, the standard values κ ₀ and ρ ₀ are used as the κ value and ρ value used for the κ OPC. If the measured modulation degree Mm0 is less than 0.98 × M0, the standard value is multiplied by α as the κ value and ρ value, and if the measured modulation degree Mm0 exceeds 1.02 × M0, the κ value and A value obtained by multiplying the standard value by β is used as the ρ value. The values of α and β can be obtained experimentally. Mm1 is the same as Mm0, and is used to improve the accuracy of numerical values of α and β by simple averaging, weighted averaging, and so on.

  Here, an example is shown in which the value of the modulation factor when the asymmetry is −5% and 0% is stored in the reference database. This is because the asymmetry and the change rate of the modulation factor with respect to the recording power are small, that is, the recording power is low. It is sufficient if the conditions are large.

  FIG. 15 is a flowchart for explaining the recording power determination method in this embodiment. The sequence shown in FIG. 15 and the standard database shown in FIG. 16 are held as programs in the memory 180 of the optical disc apparatus shown in FIG. The CPU 140 executes the sequence shown in FIG. 15 using the programs and tables stored in the memory 180.

  First, in order to start OPC, OPC parameters such as recording start power and recording end power for the disc, and recording parameters such as power scan information and storage information are acquired (S201). Next, a plurality of types of recording powers PWm are set according to predetermined conditions, and predetermined signal patterns are recorded in the trial writing area of the optical disk using each PWm (S202). In this embodiment, since an asymmetry equivalent amount (asymmetry, beta) is acquired later, the signal pattern to be recorded needs to be a random pattern or a pattern in which long marks and short marks are mixed.

  Next, the high envelope (Henv) and low envelope (Lenv) of the playback signal corresponding to each PWm is measured by playing back the area where the test was written, and defined by the expression Mm = (Henv-Lenv) / Henv The modulation degree Mm to be calculated is calculated (S203). Next, as shown in FIG. 2, the evaluation value Smn = Mm × Pwm at κ is calculated, and the relationship between the corrected recording power Pwm and the evaluation value Smn is linearly approximated in the vicinity of Mind (disc recommended modulation degree). The recording threshold power Pthr at which the modulation degree is zero, that is, the evaluation value is zero is calculated (S204).

  Next, to determine the multiplication coefficient when calculating the OPC from the recording state, instead of using the temperature from the temperature sensor as in the case of Example 1, the asymmetry equivalent amount ASYm (m is an integer) and the modulation factor Mm are acquired at the same time. To do. From the measured relationship between ASYm and Mm, the difference from the standard data held in advance is calculated, and the values of κ and ρ are acquired with reference to a table as shown in FIG. 14 (S205). Next, the optimum recording power Popt is calculated by calculating the expression Popt = κ × ρ × Pthr using the calculated recording power threshold value Pthr and the acquired κ value and ρ value (S106). Then, recording on the recording disk is performed using the optimum recording power Popt thus determined.

  This embodiment can cope with variations in temperature sensors and variations due to driving with respect to temperature changes.

  In the above, the method of detecting the change of the modulation degree based on asymmetry and changing the calculation value has been described. As another method, a method of measuring a change in asymmetry based on the modulation degree and changing the calculation value can be considered. In this case, a reference database and a conversion table for κ values and ρ values as shown in FIG. 16 may be used instead of FIG.

In the example shown in FIG. 16, asymmetry values ASY0 and ASY1 when the modulation degrees measured by the reference drive device are 35% and 40% are tabulated in the reference database as standard value asymmetry. In a mass-produced drive device, κ and ρ are changed as shown in FIG. 16 with reference to the reference database and the relationship between the measured modulation factor and asymmetry. That is, in the drive device of interest, assuming that the asymmetry when the modulation factor is 35% is ASYm0 and the asymmetry when the modulation factor is 40% is ASYm1, ASYm0 is 0.98 × ASY0 ≦ ASYm0 ≦ 1.02 ×. If ASY0 is satisfied, the standard values κ ₀ and ρ ₀ are used as the κ value and ρ value used for the κ OPC. If the measured asymmetry ASYm0 is less than 0.98 × ASY0, the standard value is multiplied by α as the κ value and ρ value. If the measured asymmetry ASYm0 exceeds 1.02 × ASY0, the κ value and ρ value A value obtained by multiplying the standard value by β is used. The values of α and β can be obtained experimentally. ASYm1 does the same as ASYm0, and is used to improve the accuracy of numerical values of α and β through simple averaging and weighted averaging.

  The method of detecting the change of the modulation degree based on the asymmetry of this embodiment and changing the calculation value, or the method of measuring the change of the asymmetry based on the modulation degree and changing the calculation value is also effective for the γ method. By changing the ρ value of Popt = ρ × Ptarget in the same manner as in FIGS. 14 and 16, the power margin at the time of recording can be made the same even if the ambient temperature is different.

  The present invention is used in a large-capacity optical disk apparatus corresponding to an optical disk having a recording layer.

Explanatory drawing of a gamma-OPC system. Explanatory drawing of κ-OPC method. The figure which shows the experimental result about the relationship between the recording power of a BD-RE disc, and each evaluation index. The figure which shows the experimental result about the relationship between the recording power of a BD-R disc, and each evaluation parameter | index. A diagram summarizing OPC methods suitable for different recording materials. Schematic diagram of the results of measuring the power margin of a BD-RE disc for each temperature, assuming that the write power obtained using the κ method is 100%. The schematic diagram which shows the structural example of the optical disk apparatus by this invention. The figure which shows an example of the table which has the multiplication coefficient of (kappa) system of this invention for every temperature. 5 is a flowchart showing an example of a recording power determination method according to the present invention. The figure which shows the relationship between a jitter and a power margin. The figure which shows the relationship between SER (Symbol Error Rate) and a power margin. The figure which shows an example of the table which has the multiplication coefficient of (gamma) system of this invention for every temperature. The figure which shows the result of having measured the relationship between an asymmetry and a modulation degree at 0 degreeC, 25 degreeC, and 50 degreeC. The figure which shows the example of the table which changes the multiplication coefficient of (kappa) system from the relationship between asymmetry and a modulation degree. 5 is a flowchart showing an example of a recording power determination method according to the present invention. The figure which shows the example of the table which changes the multiplication coefficient of (kappa) system from the relationship between asymmetry and a modulation degree.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Optical disk 101 Optical spot 110 Optical head 111 Objective lens 112 Semiconductor laser 113 Photo detector 120 Laser power / pulse controller 130 Reproduction signal processor 140 CPU
150 Servo Controller 160 Spindle Motor 170 Temperature Sensor 180 Memory

Claims (12)

Acquiring information necessary to determine the optimum recording power of the laser;
Recording a data pattern for power calibration while gradually changing the recording power based on the acquired information in the test writing area of the optical disc medium;
Calculating a modulation degree according to recording power from a reproduction signal obtained by reproducing the data pattern;
Determining a first recording power using a degree of modulation according to the recording power;
Measuring the ambient temperature of the optical disc medium;
Obtaining a multiplication coefficient according to the ambient temperature;
Possess a step of obtaining an optimum recording power by multiplying the acquired multiplication factor to the first recording power,
The first recording power is a recording threshold power Pthr, and the optimum recording power Popt is obtained by a relational expression Popt = ρ × κ × Pthr using multiplication coefficients ρ and κ, and at least of the multiplication coefficients ρ and κ. optical disc recording method characterized by one of which have a temperature dependence. Acquiring information necessary to determine the optimum recording power of the laser;
Recording a data pattern for power calibration while gradually changing the recording power based on the acquired information in the test writing area of the optical disc medium;
Calculating a modulation degree according to recording power from a reproduction signal obtained by reproducing the data pattern;
Determining a first recording power using a degree of modulation according to the recording power;
Measuring the ambient temperature of the optical disc medium;
Obtaining a multiplication coefficient according to the ambient temperature;
Multiplying the first recording power by the obtained multiplication coefficient to obtain an optimum recording power;
Have
The first recording power is a recording power Ptarget corresponding to a target of the rate of change of the modulation degree with respect to the recording power changed stepwise, and the optimum recording power Popt is expressed by a relational expression Popt = ρ using a multiplication coefficient ρ. A method of recording an optical disk, characterized in that the multiplication coefficient ρ is determined by Ptarget and has a temperature dependency. 3. The recording method according to claim 1, wherein the data pattern for power calibration is a data pattern including repetition of a longest mark and a space of a modulation code to be used. Acquiring information necessary to determine the optimum recording power of the laser;
Recording a data pattern for power calibration while gradually changing the recording power based on the acquired information in the test writing area of the optical disc medium;
Calculating a modulation factor and an asymmetry equivalent amount according to recording power from a reproduction signal obtained by reproducing the data pattern;
Determining a first recording power using a degree of modulation according to the recording power;
Collating the relationship between the degree of modulation and the asymmetry equivalent when the temperature changes with previously stored standard data, and obtaining a multiplication coefficient according to the difference from the standard data;
An optical disc recording method comprising: obtaining an optimum recording power by multiplying the first recording power by the obtained multiplication coefficient. 5. The optical disk recording method according to claim 4 , wherein the power calibration data pattern is a random pattern. 5. The optical disk recording method according to claim 4 , wherein the first recording power is a recording threshold power Pthr, and the optimum recording power Popt is obtained by a relational expression Popt = ρ × κ × Pthr using multiplication coefficients ρ and κ. And at least one of the multiplication coefficients ρ and κ is variable. 5. The optical disc recording method according to claim 4 , wherein the first recording power is a recording power Ptarget corresponding to a target of a change rate of a modulation degree with respect to the recording power changed stepwise, and the optimum recording power Popt is multiplied. An optical disk recording method, wherein the multiplication coefficient ρ is variable, which is obtained by a relational expression Popt = ρ × Ptarget using a coefficient ρ. An optical head comprising a laser light source, an objective lens for condensing the laser light from the laser light source onto an optical disk medium, and a photodetector for detecting the laser light reflected from the optical disk and incident on the objective lens;
Means for holding the OPC multiplication factor as a temperature dependent multiplication factor;
Means for recording a data pattern for power calibration while gradually changing the recording power of the laser light source in a test writing area of an optical disk medium;
Means for calculating the degree of modulation according to the recording power from the reproduction signal of the data pattern;
Means for determining a first recording power peculiar to the OPC method using a modulation degree corresponding to the recording power;
Means for measuring the ambient temperature of the optical disk medium;
A multiplication coefficient corresponding to the measured ambient temperature have a means for obtaining the optimum recording power by multiplying said first recording power,
The first recording power is a recording threshold power Pthr, and the optimum recording power Popt is obtained by a relational expression Popt = ρ × κ × Pthr using multiplication coefficients ρ and κ, and at least of the multiplication coefficients ρ and κ. one of an optical disk apparatus characterized by have a temperature dependence. An optical head comprising a laser light source, an objective lens for condensing the laser light from the laser light source onto an optical disk medium, and a photodetector for detecting the laser light reflected from the optical disk and incident on the objective lens;
Means for holding the OPC multiplication factor as a temperature dependent multiplication factor;
Means for recording a data pattern for power calibration while gradually changing the recording power of the laser light source in a test writing area of an optical disk medium;
Means for calculating the degree of modulation according to the recording power from the reproduction signal of the data pattern;
Means for determining a first recording power peculiar to the OPC system using a modulation degree corresponding to the recording power;
Means for measuring the ambient temperature of the optical disk medium;
Means for multiplying the first recording power by a multiplication coefficient corresponding to the measured ambient temperature to obtain an optimum recording power;
Have
The first recording power is a recording power Ptarget corresponding to a target of the rate of change of the modulation degree with respect to the recording power changed stepwise, and the optimum recording power Popt is expressed by a relational expression Popt = ρ using a multiplication coefficient ρ. An optical disc apparatus characterized in that the multiplication coefficient ρ is determined by Ptarget and has temperature dependence. An optical head comprising a laser light source, an objective lens for condensing the laser light from the laser light source onto an optical disk medium, and a photodetector for detecting the laser light reflected from the optical disk and incident on the objective lens;
Means for holding the relationship between the standard modulation degree and the asymmetry equivalent amount as standard data, and means for holding the relationship between the difference from the standard data and the value of the multiplication coefficient of the OPC method;
Means for recording a data pattern for power calibration while gradually changing the recording power of the laser light source in a test writing area of an optical disk medium;
Means for calculating the degree of modulation and the asymmetry equivalent amount according to the recording power from the reproduction signal obtained by reproducing the data pattern;
Means for determining a first recording power peculiar to the OPC method using a modulation degree corresponding to the recording power;
Means for collating the relationship between the degree of modulation and the asymmetry equivalent when the temperature changes with the standard data, and obtaining a multiplication coefficient according to the difference from the difference with the standard data;
Means for multiplying the first recording power by the obtained multiplication coefficient to obtain an optimum recording power. 11. The optical disc apparatus according to claim 10 , wherein the first recording power is a recording threshold power Pthr, and the optimum recording power Popt is obtained by a relational expression Popt = ρ × κ × Pthr using multiplication coefficients ρ and κ. An optical disc apparatus wherein at least one of the multiplication coefficients ρ and κ is variable. 11. The optical disk apparatus according to claim 10 , wherein the first recording power is a recording power Ptarget corresponding to a target of a rate of change of modulation with respect to the recording power changed stepwise, and the optimum recording power Popt is a multiplication coefficient. An optical disc apparatus characterized in that ρ is obtained by a relational expression Popt = ρ × Ptarget, and the multiplication coefficient ρ is variable.

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